Optoelectronic semiconductor body and light-emitting diode

ABSTRACT

A light-emitting diode includes a semiconductor body and electrical connection points for contacting the semiconductor body, the semiconductor body including an active region including a quantum well that generates electromagnetic radiation, a first region and a second region that impede passage of charge carriers from the active region, wherein the semiconductor body is based on a nitride compound semiconductor material, the first region is directly adjacent to the active region on a p-side, the second region is arranged on a side of the first region facing away from the active region, the first region has an electronic band gap larger than the electronic band gap of the quantum well and less than or equal to an electronic band gap of the second region, the first region and the second region contain aluminum, and the active region emits electromagnetic radiation having a peak wavelength of less than 480 nm.

TECHNICAL FIELD

This disclosure relates to an optoelectronic semiconductor body and alight-emitting diode having such an optoelectronic semiconductor body.

BACKGROUND

US 2008/0073658 A1 describes a semiconductor body. There is, however, aneed to provide a semiconductor body and a light-emitting diode havingsuch a semiconductor body having a particularly favorable agingbehavior.

SUMMARY

We provide an optoelectronic semiconductor body including an activeregion including a quantum well that generates electromagneticradiation, a first region that impedes passage of charge carriers fromthe active region, and a second region that impedes passage of chargecarriers from the active region, wherein the semiconductor body is basedon a nitride compound semiconductor material, the first region isdirectly adjacent to the active region on a p-side, the second region isarranged on a side of the first region facing away from the activeregion, the first region has an electronic band gap larger than theelectronic band gap of the quantum well and less than or equal to anelectronic band gap of the second region, and the first region and thesecond region contain aluminum.

We also provide a light-emitting diode including the semiconductor bodyincluding an active region including a quantum well that generateselectromagnetic radiation, a first region that impedes passage of chargecarriers from the active region, and a second region that impedespassage of charge carriers from the active region, wherein thesemiconductor body is based on a nitride compound semiconductormaterial, the first region is directly adjacent to the active region ona p-side, the second region is arranged on a side of the first regionfacing away from the active region, the first region has an electronicband gap larger than the electronic band gap of the quantum well andless than or equal to an electronic band gap of the second region, thefirst region and the second region contain aluminum, and electricalconnection points for contacting the semiconductor body, wherein thelight-emitting diode emits electromagnetic radiation having a peakwavelength of less than 480 nm.

We further provide a light-emitting diode including a semiconductor bodyand electrical connection points for contacting the semiconductor body,the semiconductor body including an active region including a quantumwell that generates electromagnetic radiation, a first region thatimpedes passage of charge carriers from the active region, and a secondregion that impedes passage of charge carriers from the active region,wherein the semiconductor body is based on a nitride compoundsemiconductor material, the first region is directly adjacent to theactive region on a p-side, the second region is arranged on a side ofthe first region facing away from the active region, the first regionhas an electronic band gap larger than the electronic band gap of thequantum well and less than or equal to an electronic band gap of thesecond region, the first region and the second region contain aluminum,and the active region emits electromagnetic radiation having a peakwavelength of less than 480 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an example of an optoelectronicsemiconductor body.

FIG. 2 is a graphical plot of the advantages of an optoelectronicsemiconductor body.

FIG. 3 is a schematic sectional illustration of an example of alight-emitting diode.

REFERENCES

-   -   1 active region    -   1 a quantum well    -   2 first region    -   3 intermediate region    -   3 a, b, c, d, e, f subregions    -   4 second region    -   5 n-type region    -   10 semiconductor body    -   11, 12 connection points    -   E1, E2, E3 a,b,c,d,e, E4 band gaps

DETAILED DESCRIPTION

We provide an optoelectronic semiconductor body. The optoelectronicsemiconductor body may, for example, be a radiation-emittingsemiconductor body used in a light-emitting diode or in a laser diode.

The optoelectronic semiconductor body may comprise an active region thatgenerates electromagnetic radiation. For this purpose, the active regioncomprises at least one quantum well, in particular a plurality ofquantum wells separated from one another by barriers. The active regioncan in particular generate UV radiation or blue light during operation.

The semiconductor body may comprise a first region that impedes thepassage of charge carriers, in particular electrons, from the activeregion. The first region is therefore a region that blocks chargecarriers, in particular electrons, from the active region so that theyare more likely to remain in the active region than they would bewithout the first region. The first region can therefore contribute tolimiting or preventing the loss of charge carriers, in particularelectrons, in the active region.

The optoelectronic semiconductor body may comprise a second region thatimpedes the passage of charge carriers, in particular electrons, fromthe active region. In other words, the optoelectronic semiconductor bodycomprises, in addition to the first region, a further region thatlikewise impedes or prevents the exit of charge carriers, in particularelectrons, from the active region. The first region and the secondregion therefore ensure, that the probability of charge carriers, inparticular electrons, leaving the active region is reduced.

The optoelectronic semiconductor body may be based on a nitride compoundsemiconductor material. Here and in the following, this entails that thesemiconductor body or at least a part thereof, particularly preferablyat least the active region, the first region and the second region,comprises or consists of a nitride compound semiconductor material,preferably Al_(n)Ga_(m)In_(1-n-m)N, wherein 0≤n≤1, 0≤m≤1 and n+m≤1. Thismaterial does not necessarily have to have a mathematically exactcomposition according to the above formula. Rather, it may have, forexample, one or more dopants and additional constituents. For the sakeof simplicity, however, the above formula only contains the essentialconstituents of the crystal lattice (Al, Ga, In, N), even if they may bepartially replaced and/or supplemented by small quantities of furthersubstances.

The first region may be directly adjacent to the active region on ap-side. That is to say that in a direction transverse or perpendicularto the main plane of extension of the semiconductor body, for example,in a direction parallel or antiparallel to the growth direction of thesemiconductor body, the first region directly follows the active region.The first region is arranged on a side of the active region facing thep-doped side of the semiconductor body and is therefore located on thep-side of the active region.

The second region may be arranged on a side of the first region facingaway from the active region. That is to say that the first region isarranged between the second region and the active region. Further layersor regions can be arranged between the first region and the secondregion. Furthermore, it is possible for the first region and the secondregion to adjoin one another directly.

The regions of the optoelectronic semiconductor body preferably extendover the entire cross section of the semiconductor body and have apredefinable thickness in a vertical direction perpendicular to the mainplane of extension of the semiconductor body.

The first region may have an electronic band gap larger than theelectronic band gap of the quantum well and smaller than or equal to theelectronic band gap of the second region. In particular, the electronicband gap of the first region is larger than the electronic band gap ofeach quantum well in the active region. Preferably, the electronic bandgap of the second region is larger than the electronic band gap of thefirst region.

The first region and the second region may contain aluminum. That is tosay that the first region and the second region are formed, for example,with AlGaN, wherein the aluminum concentration is, for example, at least2 percent, in particular at least 5 percent. The first region and thesecond region may in particular be free of indium or the concentrationof indium in these regions is very low and is, for example, less than1%. By using aluminum in the first and second regions, an electronicband gap larger than the electronic band gap of the quantum well can beset in a particularly efficient manner.

An optoelectronic semiconductor body may be specified having

an active region comprising a quantum well that generateselectromagnetic radiation,

a first region that impedes the passage of charge carriers from theactive region,

a second region that impedes the passage of charge carriers from theactive region, wherein

the semiconductor body is based on a nitride compound semiconductormaterial,

the first region is directly adjacent to the active region on a p-side,

the second region is arranged on a side of the first region facing awayfrom the active region,

the first region has an electronic band gap larger than the electronicband gap of the quantum well and smaller than or equal to the electronicband gap of the second region, and

the first region and the second region contain aluminum.

An optoelectronic semiconductor body described here is based, amongother things, on the consideration, that a suitable doping profile forthe p-type dopant of the semiconductor body enables an optoelectronicsemiconductor body that may generate electromagnetic radiation of highefficiency for long periods of time.

For this reason, it is necessary to control the diffusion of the p-typedopant or defects (e.g., point defects) in the semiconductor body in amanner enabling an efficient injection of holes into the active region,without the p-type dopant or defects or foreign atoms induced by thedoping being able to enter the p-side quantum wells.

The p-type dopant is, for example, magnesium that tends to diffuse inthe nitride compound semiconductor material-based semiconductor body andmay greatly reduce the efficiency of radiation generation when enteringthe active region.

To limit the diffusion of the p-type dopant, it would be possible, forexample, to introduce nominally undoped regions between the activeregion and the p-doped region formed with aluminum-free layers. Thedopant profile can furthermore be adjusted by a precise control of thegrowth temperatures to regulate the diffusion of the p-type dopant.Temperature fluctuations during growth of the p-side of thesemiconductor body then adversely affect efficiency and aging stability.

A semiconductor body described here is based, among other things, on therecognition that a first region containing aluminum and being arrangeddirectly on the active region and having an electronic band gap largerthan the electronic band gap of the active region may increase theconfinement of holes and electrons in the active region. The firstregion thus forms a charge carrier blocking layer, in particular also anelectron blocking layer. Furthermore, the interface defined by thetransition acts as a barrier to migrating defects or diffusing foreignatoms or dopants.

The second region having an electronic band gap equal to or greater thanthe electronic band gap of the first region, then additionallyreinforces the capture of charge carriers and may be formed, forexample, on account of a corresponding doping for injecting holes intothe active region.

The loss of charge carriers, in particular electrons, may in particularlead to a reduction in the internal quantum efficiency of the activeregion in particular for larger operating currents (so-called “droop”).This problem is reduced by the first region and the second region.

In that the first region is arranged between the second region and theactive region and has, for example, a band gap smaller than the band gapof the second region, but larger than the band gap of the quantum wellin the active region, the first region can act as a diffusion barrierfor the passage of the p-type dopant or foreign atoms or defects.

An intermediate region may be arranged between the first and secondregions, wherein the intermediate region has an electronic band gaplarger than the electronic band gap of the quantum well and smaller thanthe electronic band gap of the first region and of the second region.

In particular, the electronic band gap is larger than the electronicband gap of each quantum well of the active region. The intermediateregion thus impedes or prevents the passage of electrons from the activeregion. Furthermore, the intermediate region prevents diffusion of thep-type dopant into the active region.

In particular, it is possible for the intermediate region to bepartially or completely free of aluminum. The fact that the intermediateregion is partially free of aluminum may, in particular, mean that atleast one layer or layer sequence of the intermediate region is free ofaluminum. That is to say that no aluminum is introduced into theintermediate region during production of this layer or layer sequence.

The intermediate region may comprise at least two subregions that differfrom one another in terms of their material composition and electronicband gaps. The subregions are formed, for example, as layers, which fillthe entire cross section of the semiconductor body and have apredefinable thickness in the vertical direction.

For example, the intermediate region has five or more subregions thatdiffer in terms of their material composition at least in pairs. Forexample, two directly adjacent subregions differ with regard to theirmaterial composition, wherein subregions may border on a subregion onopposite sides having the same material composition and the sameelectronic band gap, and differ from the material composition and theelectronic band gap of the directly adjoining subregion. For example,subregions with larger and smaller band gaps can be arranged alternatelyalong the vertical direction, wherein the band gap of each subregion islarger than the band gap of the quantum well and smaller than the bandgap of the first and second regions.

The fact that the intermediate region is partially free of aluminum,may, in particular, mean that at least one subregion of the intermediateregion is free of aluminum. That is to say that no aluminum isintroduced into the intermediate region during the production of thissubregion.

The intermediate region may directly adjoin the first region and maydirectly adjoin the second region. That is to say that in verticaldirection the first region then directly follows the active region, theintermediate region directly follows the first region and the secondregion directly follows the intermediate region. This sequence ofregions ensures efficient confinement of charge carriers in the activeregion and forms an efficient barrier against diffusion of p-type dopantinto the active region.

Directly adjacent subregions of the intermediate region may differ fromone another with regard to their band gap. As a result, a plurality ofinterfaces are formed between subregions in the intermediate region atwhich a jump occurs in the band gap. Surprisingly, we found thatprecisely these interfaces between the subregions efficiently preventdiffusion of the p-type dopant, in particular the diffusion of magnesiuminto the active region.

The second region may have an aluminum concentration greater than thealuminum concentration in the first region. For example, the firstregion has an aluminum concentration greater than 5 percent. The secondregion then has an aluminum concentration greater than 5 percent, inparticular an aluminum concentration greater than 10 percent.

The second region may be p-doped. That is to say that the second regionis, for example, the region of the semiconductor body closest to theactive region which is p-doped. For example, the second region is dopedwith magnesium and has a dopant concentration of at least 1019/cm³. In afurther example, the p-type doping can be realized by alternativedopants or foreign atoms such as C, Be or the like.

The first region and, if present, the intermediate region may nominallybe undoped and/or n-doped.

Nominally undoped means that these regions of the semiconductor body arenot specifically doped during production. A p-type dopant may, however,pass into the first region and the intermediate region to a small extentby diffusion processes during the production of subsequent regions. Forexample, the concentration of the p-type dopant in the two regions isthen at most 1020/cm³. In particular, the concentration of the p-typedopant is lower than in the second region.

Alternatively or additionally, it is possible for the regions to ben-doped to a small extent. For example, the doping may be achievedduring production with silicon by adding silane (SiH₄). Thus, an n-typeco-doping takes place, which can lead to formation of a particularlysharp boundary between the n-doped region and the p-doped region of thesemiconductor body. In particular, the co-doping can impede diffusionprocesses of the p-type dopant towards the active region.

According to at least one example of the semiconductor body, the firstregion is formed with Al_(y1) Ga_(1-y1)N or withAl_(y1)In_(x)Ga_(1-y1)N, wherein y1 is >0.05 and x<0.1. The first regionhas, for example, a thickness between at least 1 nm and at most 5 nm.The intermediate region has a subregion which is formed withIn_(x)Ga_(1-x)N, wherein x>0.01 and x<0.05, wherein the subregion has,for example, a thickness of at least 0.05 nm and at most 5 nm.Furthermore, the intermediate region has a subregion formed with GaN andhas, for example, a thickness of at least 0.5 nm and at most 5 nm. Thesecond region is then formed with Al_(y2)Ga_(1-y2)N or withAl_(y2)In_(x)Ga_(1-y2)N, wherein y2>y1 and x<0.01 and the second regionhas, for example, a thickness of at least 1 nm and at most 20 nm.

Such a configuration of the first region, of the intermediate region andthe second region proves to be particularly advantageous with regard tothe confinement of charge carriers in the active region and obstructionof diffusion of the p-type dopant into the active region.

We further provide a light-emitting diode. The light-emitting diodecomprises an optoelectronic semiconductor body described herein. That isto say that all the features disclosed for the semiconductor body arealso disclosed for the light-emitting diode and vice versa. Thelight-emitting diode further comprises first and second connectionpoints designed to electrically contact the semiconductor body.

The light-emitting diode emits electromagnetic radiation having a peakwavelength of less than 480 nm during operation, in particular of lessthan 400 nm. In particular, the light-emitting diode emitselectromagnetic radiation having a peak wavelength 360 nm to 480 nm, inparticular 360 nm to 395 nm. We found that, on account of the improvedconfinement of charge carriers in the active region for one theoptoelectronic semiconductor bodies described here, the use of thesemiconductor body to generate UV radiation, in particular of UVAradiation and of blue light, is particularly advantageous.

In the following, the optoelectronic semiconductor body described hereand the light-emitting diode described here will be explained in moredetail on the basis of examples and associated figures.

Equal, identical or identically operating elements are provided with thesame references in the figures. The figures and the size ratios of theelements illustrated in the figures are not to be regarded as being toscale. Rather, individual elements may be represented with anexaggerated size for better representability and/or for bettercomprehensibility.

FIG. 1 schematically shows a band diagram for an optoelectronicsemiconductor body. The optoelectronic semiconductor body comprises anactive region 1 having at least one quantum well 1 a, in particular amultiple quantum well structure having a plurality of quantum wells. Theactive region 1 preferably comprises five identical quantum wells 1 abetween each of which a barrier is arranged. The quantum wells 1 a eachhave a thickness of, for example, 3 nm, the barriers each have athickness of, for example, 4.7 nm. The quantum wells 1 a are formed withInGaN, the barriers with AlGaN.

The first region 2 is directly adjacent to the active region 1 on thep-side. The first region 2 is formed with Al_(y1)Ga_(1-y1)N or byAl_(y1)In_(x)Ga_(1-y1)N. In this example, y1 is preferably greater than0.05 and x<0.01. The thickness of the first region is, for example, atleast 1 nm and at most 5 nm.

The intermediate region 3 directly follows the side of the first region2 facing away from the active region 1. The intermediate region 3comprises a first subregion 3 a formed with GaN, a second subregion 3 bformed with In_(x)Ga_(1-x)N, a third subregion 3 c formed with GaN, afourth subregion 3 d formed with In_(x)Ga_(1-x)N, a fifth subregion 3 eformed with GaN. In each instance, the thickness of the subregions is atleast 0.05 nm and at most 5 nm.

In this example, x is preferably greater than 0.01 and less than 0.05.The intermediate region is in particular free of aluminum.

Directly on the side of the intermediate region 3 facing away from thefirst region 2, the second region 4 is arranged, which is formed withAl_(y2)Ga_(1-y2)N or with Al_(y2)In_(x)Ga_(1-y2)N. Here, x<0.01. Y2 ispreferably greater than y1, for example, 0.06 or greater. The thicknessof the second region is at least 1 nm and at most 20 nm.

The first region 2 has an electronic band gap E2 larger than theelectronic band gap E1 of the quantum well 1 a and larger than theelectronic band gaps E3 a, E3 b, E3 c, E3 d, E3 e in the intermediateregion 3. The subregions 3 b and 3 d in the intermediate region 3 haveband gaps E3 b, E3 d smaller than the band gaps E3 a, E3 c, E3 e in thesubregions 3 a, 3 c and 3 e. However, all band gaps in the intermediateregion 3 are larger than the band gap of the quantum well 1 a.

In the second region 4, the semiconductor body has a band gap E4 greaterthan the band gap in all other regions and greater than the band gap E1in the quantum well.

The schematic plot of FIG. 2 shows the intensity of the emitted light ofa light-emitting diode having an optoelectronic semiconductor bodyplotted against the operating time t and normalized to the intensity atthe time t=0. The curve c is a plot for a semiconductor body, whereasthe curves b and a are comparative curves for semiconductor bodies whichdo not have the first region 2 and the intermediate region 3. The p-sideof the semiconductor body of curve b was produced at a lower growthtemperature, than the p-side of the semiconductor body of the curve a.This leads to a reduced diffusion of magnesium into the active region 1during production. After about 500 operating hours, however, thispositive effect is no longer detectable (not shown).

As can be seen from the graphical plot, the intensity of the generatedlight of our semiconductor body hardly changes over time. That is to saythat the semiconductor body has a particularly favorable aging behavior,which can be attributed in particular to the improved doping profilewith the p-type dopant, the improved confinement of charge carriers inthe active region and the reduced diffusion of dopant into the activeregion both during production and during operation.

FIG. 3 shows a schematic illustration of a light-emitting diode having asemiconductor body 10. In addition to the described regions, thelight-emitting diode comprises an n-conducting region, which iselectrically contacted, for example, via the first connection point 11.The second connection point 12 is located on the opposite side of thesemiconductor body 10, via which the semiconductor body is connected,for example, on the p-side.

During operation, the light-emitting diode generates electromagneticradiation having a peak wavelength of less than 480 nm, in particular ofless than 400 nm. We found that, on account of the improved confinementof charge carriers in the active region for one the optoelectronicsemiconductor bodies described here, the use of the semiconductor bodyto generate UV radiation, in particular of UVA radiation, isparticularly advantageous. The light-emitting diode is then alight-emitting diode emitting UV radiation.

Our semiconductor bodies and light-emitting diodes are characterized inparticular by the following advantages:

The semiconductor body exhibits a higher tolerance to temperaturefluctuations during production of the p-doped side of the semiconductorbody since the described regions effectively suppress a diffusion of thep-type dopant into the active region. The probability for a diffusion ofthe p-type dopant into the active region is thus reduced.

Furthermore, the injection of holes in a semiconductor body is improvedin contrast to a semiconductor body without the regions. The outflow ofelectrons from the active region is also strongly suppressed for anactive region having a low indium concentration, as is used inparticular to generate UV radiation, due to the regions of thesemiconductor body described here.

Our LEDs and semiconductor diodes are not restricted to the examples bythe description on the basis of the examples. Rather, this disclosureencompasses any new feature and also any combination of featuresincluding in particular any combination of features in the appendedclaims, even if the feature or combination itself is not explicitlyspecified in the claims or examples.

Priority of DE 10 2016 111 929.6 is claimed, the subject matter of whichis incorporated herein by reference.

What is claimed is:
 1. A light-emitting diode comprising: asemiconductor body and electrical connection points for contacting thesemiconductor body, the semiconductor body comprising an active regioncomprising a quantum well that generates electromagnetic radiation, afirst region that impedes passage of charge carriers from the activeregion, and a second region that impedes passage of charge carriers fromthe active region, wherein the semiconductor body is based on a nitridecompound semiconductor material, the first region is directly adjacentto the active region on a p-side, the second region is arranged on aside of the first region facing away from the active region, the firstregion has an electronic band gap larger than the electronic band gap ofthe quantum well and less than or equal to an electronic band gap of thesecond region, the first region and the second region contain aluminum,the active region emits electromagnetic radiation having a peakwavelength of less than 480 nm, the first region is n-doped and thesecond region is p-doped.
 2. The light-emitting diode according to claim1, further comprising an intermediate region arranged between the firstregion and the second region, wherein the intermediate region has anelectronic band gap larger than the electronic band gap of the quantumwell and smaller than the electronic band gaps of the first region andof the second region, and the intermediate region is at least partiallyfree of aluminum.
 3. The light-emitting diode according to claim 2,wherein the intermediate region has at least two subregions that differfrom one another in their material composition and electronic band gap.4. The light-emitting diode according to claim 3, wherein at least oneof the subregions is free of aluminum.
 5. The light-emitting diodeaccording to claim 2, wherein the intermediate region directly adjoinsthe first region and directly adjoins the second region.
 6. Thelight-emitting diode according to claim 3, wherein directly adjoiningsubregions of the intermediate region have different band gaps from eachother.
 7. The light-emitting diode according to claim 1, wherein thesecond region has an aluminum concentration greater than an aluminumconcentration in the first region.
 8. The light-emitting diode accordingto claim 2, wherein the intermediate region is nominally undoped.
 9. Thelight-emitting diode according to claim 2, wherein the intermediateregion is n-doped.
 10. The light-emitting diode according to claim 1,wherein the active region emits electromagnetic radiation having a peakwavelength between 360 nm and 395 nm.
 11. The light-emitting diodeaccording to claim 1, wherein the second region is formed withAl_(y2)Ga_(1-y2)N or with Al_(y2)In_(x)Ga_(1-y2)N, and x is smaller than0.01, Y2 is 0.06 or greater.
 12. The light-emitting diode according toclaim 1, wherein a thickness of the second region is 1 nm to 20 nm. 13.The light-emitting diode according to claim 1, wherein the first regionis formed with Al_(y1)Ga_(1-y1)N or Al_(y1)In_(x)Ga_(1-y1)N, and y1 isgreater than 0.05 and x is smaller than 0.01.
 14. The light-emittingdiode according to claim 1, wherein a thickness of the first region is 1nm to 5 nm.
 15. The light-emitting diode according to claim 1, whereinthe first region is formed with Al_(y1)In_(x)Ga_(1-y1)N, the secondregion is formed with Al_(y2)In_(x)Ga_(1-y2)N, x is greater than 0 andsmaller than 0.01, and Y2 is greater than y1.
 16. A light-emitting diodecomprising: a semiconductor body and electrical connection points forcontacting the semiconductor body, the semiconductor body comprising anactive region comprising a quantum well that generates electromagneticradiation, a first region that impedes passage of charge carriers fromthe active region, and a second region that impedes passage of chargecarriers from the active region, wherein the semiconductor body is basedon a nitride compound semiconductor material, the first region isdirectly adjacent to the active region on a p-side, the second region isarranged on a side of the first region facing away from the activeregion, the first region has an electronic band gap larger than theelectronic band gap of the quantum well and less than or equal to anelectronic band gap of the second region, the first region and thesecond region contain aluminum, the active region emits electromagneticradiation having a peak wavelength of less than 480 nm, and the firstregion is nominally undoped.